Many trucks, particularly those hauling loose loads such as sand and gravel, need a truck cover to prevent the wind from blowing load particles off the load bed. Various apparatus have been devised for covering a truck load. Some such apparatus include a motor for selectively winding a flexible cover. My U.S. Pat. No. 5,031,955 provides a truck cover which may be conveniently motor operated from the cab of a truck while simultaneously extending the cover over the truck bed and pressing down on the front of the cover proximate a winding assembly which winds up the cover at the front of the truck bed. Similarly, U.S. Pat. No. 5,238,287 shows a front mount telescopic arm truck cover system, and U.S. Pat. No. 5,524,953 shows a contractible vehicle bed cover assembly with an extendable closure.
Container trucks, however, present special problems. In particular, such container trucks tend to have differently sized beds, and are required to accept containers of different dimensions. To accommodate these variances, the arms normally used in conventional truck bed covers have to be long enough to reach from their mounting point to both the front and rear ends of the truck bed. U.S. Pat. No. 5,292,169 shows such a truck container cover. Not only do such arms require great effort to move from either their forward most or rearward most position, but they are not able to efficiently accommodate containers of different sizes.
U.S. Pat. No. 5,752,735 shows one attempt to address at least this latter problem with adjustable pivot points shifted along opposite rails by hydraulic cylinders. This design, however, uses rephasing cylinders which furthermore are not arranged in line with the rails.